A molecule (X) has (i) four sigma bonds formed by the overlap of $sp^2$ and orbitals (ii) one sigma bond formed by $sp^2$ and $sp^2$ orbitals and (iii) one $\pi$ bond formed by $P_x$ and $P_z$ orbitals. Which of the following is X?

$\begin {array} {1 1} (a)\;C_2 H_6 & \quad (b)\;C_2 H_3 CL \\ (c)\;C_2H_2CL_2 & \quad (d)\;C_2 H_4 \end {array}$

$(d)\;C_2 H_4$